Microtome knife stroppers



Dec. 8, 1959 H. ETTMAN 2,915,854

MICROTOME KNIFE STROPPERS Filed March 28, 1957 FIG.2

INVEN TOR.

BYHENRY L. ETTMAN Q w n Emil,

6 FIG. 3 ATTORNEY United States Patent Orifice 2,915,85 Patented Dec. 8, 1959 MICROTOME KNIFE STROPPERS Henry L. Ettman, Clayton, M0. Application March as, 1957, Serial No. 649,129

'3 Claims. c1. 51-102 This invention relates in general to grinding, and more particularly, to a stropping wheel for microtome knives. For the constant, efficient operation of microtomes, in

hospitals, laboratories, and clinics, for sectioning of pre- 1 pared tissue, as frozen or celloidin or paraffin-mounted, it is imperative that the knives therefor be maintained in a state of highly refined sharpness requisite for slicing sections having a thickness in the order of five microns or less. Heretofore, after a microtome knife had been ground it had been customary to subject same to manual stroking across an elongated leather strop to remove the burr or wire at the edge. This stropping or honing operation, which is substantially identical to the widely practiced domestic procedure for sharpening a straight razor for shaving, entails the use of a device for supporting at its ends a length of horizontally presented leather or related material so that an operator may by hand move the microtome knife thereacross reciprocatingly until the desired edge has been attained. However, such generally accepted hand stropping has quite understandably numerous disadvantages, among which is primarily a lack of uniformity in the stropped edge, with consequent want of uniformity in thickness of sections severed thereby. Since such operation is performed by hand the proficiency and skill of the individual will relate directly to the quality of fineness of the edge, and furthermore, there has been conclusively shown that hand stropping is effective only where the grain size of the abrasive incorporated in the leather falls within a susbtantially narrow range of relatively large size particles. Hence, fine abrasives so necessary for finishing the edge for cutting sections of marked thinness are not effectively used in a hand stropper.

In view of the required developed skill of the individual doing the stropping, hospitals, laboratories, and the like, have of necessity caused their microtome knives to be periodically transferred to some agency engaged in the microtome knife stropping service with the attendant costliness therefor.

Therefore, it is an object of the present invention to provide a motor driven knife stropping device capable of reliably and consistently applying an edge of maximum refinement and uniformity to microtome knives, skin grafting knives, and the like, and the operation of which does not require skilled personnel.

It is another object of the present invention to provide It is an additional object of the present invention to provide a microtome knife stropper which is durable in operation; which is economical in production; and which may be speedily and etficiently operated so as to conveniently assure prompt readiness for use of microtome knives.

These and other detailed objects are obtained by the structures illustrated in the accompanying drawing, in which Figure 1 is a perspective view of a microtome knife stropper constructed in accordance with and embodying the present invention.

Figure 2 is a vertical transverse section taken on the line 2-2 of Figure 1.

Figure 3 is a vertical transverse section taken on the line 33 of Figure 1.

Figure 4 is an enlarged detail illustrating the contact between the wheel and the knife to be stropped thereby.

Referring now by reference characters to drawing, A designates a microtome knife stropping machine incorporating a rectangular housing 1 having end walls 2, 2, side Walls 3, 3, a bottom wall 4, and being open in its upper portion as at 5 except for an inturned marginal flange 6. Extending through tapped openings in flange 6 at the corners of housing 1 are fixed screws 7, the upper ends thereof beingthreaded through aligned openings in a top closure plate 8, and being engaged by cap nuts 7'. Provided upon each screw 7 between flange 6 and plate 8 is an adjusting collar 9, upon selected operation of which the disposition of top plate 3 with respect to housing 1 may be altered for purposes presently appearing. Thus, for example, collars 9 on an adjacent pair of screws 7 may be adjusted relatively to the remaining collars so as to cause the top plate to be horizontally inclined, or, manifestly, all collars 9 may be regulated for raising or lowering of said plate 8 within the range provided by the available length of screw 7.

Disposed within housing 1 is a prime mover or motor M connected to a source of power external of housing 1 as by leads indicated at 10; there being an operating switch 11 connected to said motor and positioned for convenient presentation of its toggle arm upon the outer surface of end wall 2. Motor M comprises a drive shaft 12 having mounted on its outer end a pulley 13 about which i through a small, slot-like opening 19 formed in closure plate 8; said opening 19 being slightly greater than the thickness of wheel 18. I

Secured or otherwise fixed on the upper surface of closure plate 8 is a pair of spaced apart guide members 20, 20 cooperating to form a way for-a slide 21 which is centrally slotted, as at 22, for extension therethrough of a screw 23 rigid in plate 8 and having a retaining wing nut 24 threaded on its upper projecting end so that upon loosening of wing nut 24 slide 21 is freed for movement t relatively between members 20, 20 and upon tightening of said nut '24 said slide 21 will be maintained in selected position. Guide members 24], 20 are so presented as to define the path of movement of slide 21 along an axis substantially tangentially aligned with, or parallel to the tangent of, the upper portion of wheel 18 extending through opening 19.

Mounted on the end of slide 21, perpendicular thereto, and proximate wheel 18, is an elongated microtome knife holder 25 extending almost from end to end of clo sure plate 8. Said holder 25 is of a generally stepped vital for innumerable analyses. tween knife and strop had up to the; present, been; considered unattainable by any agency other than the; well knownv elongatedrazor-type strop and accounts forr the. "continued adherence to the utilization of thesarnez, However,.it hasbeen found that a wheel having a diame-q eter of, at least. eight inches, will provide in its-circum---:

configuration having a lower step or knife support ledge 25? planar-wise parallel to closure plate 8, and a riserlike abutment 25". As the thickness of wheel 18 is less than the length of microtome'knives to'be serviced by machine A, a microtome knife must, perforce, be moved by the operator along support ledge 25" so as. to present. the entire edge portion of the'knife to the wheel 18-..- In the drawing K indicates a, rnicrotome knife beingfl. provided with the conventional back 26 which may be;,'

retained upon the knife during stropping.

4. to wheel 18, and then to turn knife K over to presentthe opposite surface of the cutting edge for stropping.

As will now be developed, the speed of rotation of Wheel 18 and the range of grain size of abrasives utilized therewith has been found to fall within certain relatively well defined ranges, with a definite correlation therebetween. With respect to the angularvelocity or speed of grinding wheel 18 it has been foundthat an average such as Indented or otherwise inscribed upon the upper sunface of closureplate A space-d from knife holder 25v and axially parallel therewith is a guide line 27 so related to stropping wheel 18 as-to be aligned withthe remote; terminus of the flat curve (to be described) at. the;

extreme projecting portion. thereof. Thus, knife holder 25 will 55 adjustedly disposed so that: the; edge of a knife to be. stropped, and supported} thereon, will; be in alignment with guide line 27 by whichcondition. proper address of the knife K to wheel 18 is certain. V

In. the stropping of rnicrotorne knives it is critical that.

the cutting edge portion thereof be disposed flatwise upon the strop-,-just aswith the typical hand strops heretofore used, in order to attain substantial uniformity of striae tions in. such edge. resulting edge will be irregular and hence unproductive:

- in. usage of sections of uniform thickness, and obviously;-

unfit for providing that degree of thinness in sectionsso; This vital contact he:

ference' acurveof such angle as to be substantially co-= incident in extent with. the edge portion of the microtome knives) andsubstantially coincident with its-chord";

so astQ provide, what might be termed a fiat curve, and; thereby assure the critical engagement with the, knife. over the necessary surface thereof. for, attaining the requisite pticallydetermined stropped edge. Thus, Fig;-

me 4 of the drawing illustrates this contact ,between the. face off wheel;1 8 and. the edge of knife The iml-s,

portanceof'this feature will be apparent when it isrrecogmzed: that heretofore theproper presentation of micro. tome 1 knives to stropswas. attained through. the. devel-.-

' DPC QP 'OfiCiencyand skill oftheoperator and, obviously,

the interjection ofhuman error-was a constantlypresenh factor With the present invention, the proper engages: ment will. atall timesbe reliably effected so that the;

" stroppingfoperation will unfailingly produce the desired;

results.

The. angleof the bevelfof the cutting edge on knifeqK-c may throughthe. operationofmachine A be of any;de.-; sireddegree, with the relationship between closure plate." 8 and wheel 18 being determinative, as bythe selectedi.

positioning of closure plate 8 through use ofcollars= 9.

Thus, as closure plate 8 together with knife holder 25:

thereon, is relatively raised,..a reduced portion of wheelv the desired degreeofb'ev'el, need onlyslide knife K- along step 25so as to present one surfaceiof the edge pprtion:

Without such flat presentmennthe' to provide a thousand'feet per minute of wheel surface will provide the best results. Thus, a speed of between 400 and 700 revolutionsper minute for use with diamond base abrasives within the range of. 600 to 25,000 mesh,

is competent to provide the maximum effectiveness. It has been found that within a speed range of 700 to 1200 revolutions per minute an effective abrasive is alumina which is slightly less hard than diamonds and which in i this i'nstance would preferably be from .1 to .3 microns.

Other abrasives, such as silicon carbide, fused A1 0 e.g,

Alundun (-being' a trademark of the Norton Co; for fused alumina-l up to-1,000 mesh and between a speed of- 800 and 2000 revolutionsper minute have been found J: equally effective forthe stropping' operation herein;

' If must be recognized that the drive connectiom betweenmotorand'wheel '1 8 may be easily controlled by any well k-now-n expedients so asto provide the de' sired speed for the particular graim size of abrasive on I Stropping'wheelsof-"the type incorporated in the present inventiommay' be formed of a plywood base or'any other-like durable material with the periphery thereof l covered' with leather, such aseven grained cordovan or 1 otherwelllinownsmaterial capable of receiving abrasives-- The abrasives utilized with.wheel 18 are preferably of a diamond 'base butmay be ofsilicon= carbide orth'e like,

and, as sug-gested above, should have a-mesh size fallingwit-hin' tlie=range=of600 to 25,000.. Also, abrasives-within a thisranger'nay vary in hardness within a comparable range; 1 I

-He'retofore-with hand strops there was a-definite l mitatiOn oh thefine'ness of. the abrasives which could he effectively utilized therewith, such abrasives defining a relatively narrow range of about 600-try l200 m'esh Abrasives exceeding that range in fineness-could not be practically utilized" astheknife would have had-to be moved relatively more rapidly across the st'r'op than couldbe reliably effected by-handl WithLthe presenta invention-grain sizes ranging in finenessup tof25',000

H the cuttingsedge'upon the knife'being stropped will h'ave a;un'rformityas to extent of striations' -forn-1'ed jointly" thereintby the initial i grinding and subsequent stropping' operations, with the result that sections cutthereby will Hand stroppedmesh may be incorporated in-wheel 18"as -the=latterfrnay be rotated at speeds necessary for use of abrasives re-" sulting in edges of'extreme fineness, capable of severing sections ofa degree of thinness hitherto. -beyond the'competency-of rnicrotome knives manually st-ropped." The '*speediofirotationofwheel 18 wil-lb'e regulated-within thestated range for correspondence to -the particular grain size, as the finer the grain thev greater the speed;

The. operation of machine" Ans such as to assure-that have a like uniformity of thickness;- microtorne: knives consistently have; by' dint of I human errorli implicit in the: hand operation}. a variationinsharpness, as the. desired-uniformity v in the edgestr ations is necessarily": lacking, so thatsections' cut-thereby are-- similarly devoid of uniformity in thickness andhave, what-rrnightthe-described as,--a waxyeifect. These 1mperfectionsi had up." to the present 2 time 'been reluctantly accepted-masFancunvarying condition; Such lack of -'uni forn'lityi bys hand. stroppingi was customarilyaggravated whenrelatively. hard ,itcoars'e iabrasivesWereutilized, such asaneeded imstroppingia1knife-for the cuttingof reason-- I 1 ably-hard dense-sections; H a i g T in view of the foregoing it is seen that-;tl1e ma chine of the present invention has been designed to provide the necessary relationship between the stropping surface and the blade being serviced, and also to operate at such speeds as to render it capable of incorporating abrasives falling within a very broad range of size as well as density so that a controlled cutting edge obtained by use of machine A; which edge shall be of the utmost refinement and adapted both as to thickness of section as well as hardness of the same.

As shown hereinabove, machine A is so devised as to operate in a consistently reliable manner; which does not necessitate the services of highly skilled and trained individuals but which, by the nature of its constituent parts and the specific relationship thereof, will consistently assure that the requisite highly finished cutting edge will at all times be provided.

Although stropping wheels having a diameter of eight inches have been found competent to effect the desired flat engagement with the cutting edge of microtome knives of widely used size, it is to be recognized that if machine A is to be utilized with knives of relatively increased size the particular stropping wheel will accordingly necessarily be of greater diameter so as to present a curve of requisite flatness for the particular extent of cutting portion to be serviced. A wheel of 8 inches as shown herein has been found to be of generally wide and practical use, but wheels of greater size are within the comprehension of this invention so as to achieve the proper relationship with larger knives.

It should be understood that changes and modifications in the formation, construction, arrangement, and combination of the several parts of the microtome knife stropper may be made and substituted for these herein shown and described without departing from the nature and principle of my invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a stropping machine for microtome knives, the improvement comprising a wheel having a diameter of no less than eight inches whereby the circumferential curve of contact with a microtome knife to be stropped will be substantially coincident in extent with the edge portion of the knife and with the chord of such curve, means for rotating said wheel in a direction away from the knife edge portion, a peripheral covering of cordovan leather for said wheel, diamond-base abrasives embedded within said cordovan leather peripheral covering and having a fineness within the range of 14,000 to 25,000 mesh, said wheel being designed for rotation within the range of 750 to 1,000 revolutions per minute, with the velocity within such range being inversely proportional to the mesh size of the abrasive.

' chord of such curve, a peripheral covering of cordovan leather provided on said wheel, diamond-base abrasives imbedded within said cordovan leather peripheral covering and having a fineness within the range of 14,000 to 25,000 mesh, spaced guideways provided on the upper surface of said closure plate, a slide body disposed within said guideways for slideable movement therealong, the axis of said slide body being coincident with a line tangential to the projecting portion of said wheel, a microtome knife holder mounted on the end portion of said slide body proximate the projecting portion of sa d Wheel and being axially normal to said slide body, said holder having a support ledge extending from end to end thereof on its face confronting said wheel, an abutment surface extending upwardly from said ledge and being coextensive therewith and means provided in sald casing for effecting rotation of said wheel in a d1rect1on away from the knife edge portions. i

3. A microtome stropping machine as describedin claim 2 wherein means are provided for maintaining said slide body in selected position with respect to the guideways, adjustment means being provided for regulating the height of the closure plate with respect to the upper edge of the casing, and wherein the support ledge of the knife holder is in planar parallel relation to the upper surface of the closure plate.

References Cited in the file of this patent UNITED STATES PATENTS 285,559 Bishop Sept. 25, 1883 403,648 Com-sen May 21-, 1887 521,646 Dutton June 19, 1894 604,569 Ringstrom May 24, 1898 667,300 Dilg et a1. Feb. 5, 1901 1,192,709 Tone July 25, 1916 1,900,158 Butler Mar. 7, 1933 1,923,719 Fuller et a1 Aug. 22, 1933 2,052,837 Makarofi Sept. 1, 1936 2,337,718 Hoppes Dec. 28, 1943 2,579,680 Leighton Dec. 25, 1951 

